Nickel etching and plating bath

ABSTRACT

A process for plating nickel onto a nickel surface comprising first etching said nickel surface by anodic treatment in a bath, and then electroplating in the same bath. The bath is comprised of nickel chloride, nickel sulfate and boric acid to which are added small amounts of a brightener and a wetting agent.

United States Patent Emil Toledo Natick, Mass.

Sept. 4, 1969 Jan. 11, 1972 The United States of America as representedby the Secretary of the Navy Inventor Appl. No. Filed Patented AssigneeNICKEL ETCHING AND PLATING BATH 2 Claims, No Drawings US. Cl 204/32 R,204/49 Int. Cl C23b 3/02 Field of Search 204/32 R, 33, 49,141, 325, 34,20, 30

References Cited UNITED STATES PATENTS 6/1942 Wesley et al 204/34 4/1940Lindetal 2,198,268 204/49 2,299,054 10/1942 Harshaw et al. 204/14]2,702,785 2/1955 Eyerund 204/33 OTHER REFERENCES Smith, R. S. NickelPlating Directly onto Aluminum, IBM Technical Disclosure Bulletin. Vol.9, No. 8, January 1967.

Primary Examiner-John H. Mack Assistant Examiner-W. l. SolomonAtt0rneys- Edgar J. Brower, H. H. Losche and Paul S.

Collignon ABSTRACT: A process for plating nickel onto a nickel surfacecomprising first etching said nickel surface by anodic treatment in abath, and then electroplating in the same bath. The bath is comprised ofnickel chloride, nickel sulfate and boric acid to which are added smallamounts of a brightener and a wetting agent.

NICKEL ETCI-IING AND PLATING BATH BACKGROUND OF THE INVENTION Thepresent invention relates to a process for electroplating nickel onto anickel surface and has particular utility in applying a nickel coatingonto a nickel coated printed circuit board.

One of the major problems that must be overcome to obtain good adhesionon a nickel coated printed circuit board is the removal of its passivenickel oxide coating in a manner which will not affect its thin nickelcoating. Most mild-cleaning methods, such as a HCl dip, do notcompletely remove the oxide coating and more active cleaning methods,such as electroetching and electropolishing can damage the thin nickelcoating on the printed circuit board.

Conventional baths and processes for electroplating nickel are describedin Principles of Electroplating and Electroforming, by Blum andHogaboom, pages 362-381, revised third addition, 1949, McGraw-Hill BookCo., Inc., New York; and in Modern Electroplating," edited by A. G.Gray, the Electrochemical Society, 1953, pages 299-355. Almost all bathsfor electroplating nickel contain nickel sulfate, a chloride, such asnickel chloride, a buffering agent, such as boric acid, and a wettingagent such as sodium lauryl sulfate, sodium lauryl ether sulfate orsodium 7-ethyl-2-methyl-4-undecanol sulfate. Such baths include thewell-known Watts bath and other baths containing, as the source of thenickel, a combination of nickel fluoborate with nickel sulfate andnickel chloride, or a combination of nickel fluoborate with nickelchloride.

Various methods have been employed in the past to cleanse the nickeloxide film from a part which is to receive subsequent plating. In U.S.Pat. No. 2,299,054, which was issued Oct. 13, 1942, to William J.Harshaw and Kenneth E. Long, there is described an anodic-cathodictreatment for preparing a nickel plated article for chromium plating.The nickel plated article is placed in an aqueous solution of sodiumcyanide and connected as an anode while passing an electric currenttherethrough as a voltage of from 2 to 10 volts for a period of about 1second. The current is then reversed, by connecting the piece as acathode for a few seconds.

Another anodic method for cleaning nickel is described in U.S. Pat. No.3,362,894, which issued Jan. 9, 1968, to William A. Pennington andStephen D. Cramer. In this patent, a cleaning method for nickel isdescribed wherein a metal substrate is given an anodic treatment in aconcentrated aqueous solution of a lithium halide. The metal substrateis then rinsed and plated in a conventional plating bath.

SUMMARY OF THE INVENTION The present invention provides an improvedprocess for plating nickel onto a nickel surface by providing a bathwhich serves as both a cleaning bath and a plating bath. The article isfirst reverse plated, that is, the article is immersed as anode in thebath and, after about 1 minute of current application, the

current flow is reversed and the article is connected as cathode in thebath. Plating is accomplished in the normal manner. The bath is a nickelsulfate-nickel chloride bath to which a buffering agent, a brightener,and a wetting agent are added.

DESCRIPTION OF THE PREFERRED EMBODIMENT ticing the present invention.

EXAMPLE I A nickel coated printed circuit board having an area of 1.7square inches was prepared for plating by first cleaning. The articlewas degreased in a methanol rinse and then dipped in an acid bath (50percent I-ICI dip at about F The plating bath was comprised as follows:

Nickel chloride 10 ozJgal. Nickel sulfate 30 oz./gal. Boric acid 5oz./gal. Saccharine 0.1 oz./gal. Sodium lauryl sulfate 0.0] oz./gal.Temperature I60 F.

A nickel coated printed circuit board was reverse plated for 1 minute at500 ma. in the plating bath and then plated at 500 ma. for 1 hourwithout removing the circuit board from the plating bath after reverseplating.

Bend tests and metallurgical examinations revealed the plated producthad excellent adhesion. Leads were welded to the plated product and pulltests were conducted by pulling on the leads both parallel andperpendicular to the surface. Metallographic examination revealed thatadhesion between nickel layers was satisfactory.

I claim:

1. A process for electroplating nickel onto a thin nickelcoated surfaceon a printed circuit board comprising first removing oxide coating fromsaid nickel-coated surface by reverse plating in a bath with saidnickel-coated surface being connected as anode and then plating in thesame bath with said nickel-coated surface being connected as cathode,said bath consisting of about 10 oz./gal. of nickel chloride, about 30oz./gal. of nickel sulfate, about 5 oz./gal. of boric acid, about 0.1oz./gal. of saccharine, about 0.0l oz./gal. of sodium lauryl sulfate andthe balance of water.

2. The process as set forth in claim I wherein said reverse plating iscarried on for about 1 minute and said plating is carried on for about60 minutes.

2. The process as set forth in claim 1 wherein said reverse plating iscarried on for about 1 minute and said plating is carried on for about60 minutes.